From: Daniel Borkmann <daniel@iogearbox.net>
To: Yonghong Song <yhs@fb.com>, Wenbo Zhang <ethercflow@gmail.com>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>
Cc: "ast@kernel.org" <ast@kernel.org>,
"bgregg@netflix.com" <bgregg@netflix.com>,
"andrii.nakryiko@gmail.com" <andrii.nakryiko@gmail.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH bpf-next v13 1/2] bpf: add new helper get_fd_path for mapping a file descriptor to a pathname
Date: Tue, 17 Dec 2019 20:39:29 +0100 [thread overview]
Message-ID: <a8a763e2-65d2-7c71-e99d-ffae1523f0f0@iogearbox.net> (raw)
In-Reply-To: <f54e3df6-626f-e9c4-f2c2-a63fb9953944@fb.com>
On 12/17/19 5:29 PM, Yonghong Song wrote:
> On 12/17/19 1:47 AM, Wenbo Zhang wrote:
[...]
>> + * On failure, it is filled with zeroes.
[...]
>> */
>> #define __BPF_FUNC_MAPPER(FN) \
>> FN(unspec), \
>> @@ -2938,7 +2964,8 @@ union bpf_attr {
>> FN(probe_read_user), \
>> FN(probe_read_kernel), \
>> FN(probe_read_user_str), \
>> - FN(probe_read_kernel_str),
>> + FN(probe_read_kernel_str), \
>> + FN(get_fd_path),
>>
>> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>> * function eBPF program intends to call
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index e5ef4ae9edb5..43a6aa6ad967 100644
>> --- a/kernel/trace/bpf_trace.c
>> +++ b/kernel/trace/bpf_trace.c
>> @@ -762,6 +762,71 @@ static const struct bpf_func_proto bpf_send_signal_proto = {
>> .arg1_type = ARG_ANYTHING,
>> };
>>
>> +BPF_CALL_3(bpf_get_fd_path, char *, dst, u32, size, int, fd)
>> +{
>> + int ret = -EBADF;
>> + struct file *f;
>> + char *p;
>> +
>> + /* Ensure we're in user context which is safe for the helper to
>> + * run. This helper has no business in a kthread.
>> + */
>> + if (unlikely(in_interrupt() ||
>> + current->flags & (PF_KTHREAD | PF_EXITING))) {
>> + ret = -EPERM;
>> + goto error;
>> + }
>> +
>> + /* Use fget_raw instead of fget to support O_PATH, and it doesn't
>> + * have any sleepable code, so it's ok to be here.
>> + */
>> + f = fget_raw(fd);
>> + if (!f)
>> + goto error;
>> +
>> + /* For unmountable pseudo filesystem, it seems to have no meaning
>> + * to get their fake paths as they don't have path, and to be no
>> + * way to validate this function pointer can be always safe to call
>> + * in the current context.
>> + */
>> + if (f->f_path.dentry->d_op && f->f_path.dentry->d_op->d_dname) {
>> + ret = -EINVAL;
>> + fput(f);
>> + goto error;
>> + }
>> +
>> + /* After filter unmountable pseudo filesytem, d_path won't call
>> + * dentry->d_op->d_name(), the normally path doesn't have any
>> + * sleepable code, and despite it uses the current macro to get
>> + * fs_struct (current->fs), we've already ensured we're in user
>> + * context, so it's ok to be here.
>> + */
>> + p = d_path(&f->f_path, dst, size);
>> + if (IS_ERR(p)) {
>> + ret = PTR_ERR(p);
>> + fput(f);
>> + goto error;
>> + }
>> +
>> + ret = strlen(p) + 1;
>> + memmove(dst, p, ret);
>> + fput(f);
>> + return ret;
>> +
>> +error:
>> + memset(dst, '0', size);
You fill it with 0x30's ...
>> + return ret;
>> +}
next prev parent reply other threads:[~2019-12-17 19:39 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-19 13:27 [PATCH bpf-next v10 0/2] bpf: adding get_file_path helper Wenbo Zhang
2019-11-19 13:27 ` [PATCH bpf-next v10 1/2] bpf: add new helper get_file_path for mapping a file descriptor to a pathname Wenbo Zhang
2019-11-23 3:18 ` Alexei Starovoitov
2019-11-23 4:43 ` Al Viro
2019-11-23 4:51 ` Al Viro
2019-11-23 5:19 ` Alexei Starovoitov
2019-11-23 5:35 ` Al Viro
2019-11-23 6:04 ` Alexei Starovoitov
2019-12-13 19:51 ` Brendan Gregg
2019-12-05 4:20 ` [PATCH bpf-next v11 0/2] bpf: adding get_file_path helper Wenbo Zhang
2019-12-05 4:20 ` [PATCH bpf-next v11 1/2] bpf: add new helper get_file_path for mapping a file descriptor to a pathname Wenbo Zhang
2019-12-05 7:19 ` Alexei Starovoitov
2019-12-05 9:47 ` Wenbo Zhang
2019-12-15 4:01 ` [PATCH bpf-next v12 0/2] bpf: adding get_file_path helper Wenbo Zhang
2019-12-15 4:01 ` [PATCH bpf-next v12 1/2] bpf: add new helper get_file_path for mapping a file descriptor to a pathname Wenbo Zhang
2019-12-15 16:05 ` Yonghong Song
2019-12-17 6:26 ` Wenbo Zhang
2019-12-17 6:33 ` Yonghong Song
2019-12-15 16:10 ` Yonghong Song
2019-12-17 6:27 ` Wenbo Zhang
2019-12-16 22:09 ` Brendan Gregg
2019-12-17 4:05 ` Wenbo Zhang
2019-12-17 9:47 ` [PATCH bpf-next v13 0/2] bpf: adding get_fd_path helper Wenbo Zhang
2019-12-17 9:47 ` [PATCH bpf-next v13 1/2] bpf: add new helper get_fd_path for mapping a file descriptor to a pathname Wenbo Zhang
2019-12-17 16:29 ` Yonghong Song
2019-12-17 19:39 ` Daniel Borkmann [this message]
2019-12-18 0:11 ` Wenbo Zhang
2019-12-18 0:06 ` Wenbo Zhang
2019-12-18 0:56 ` [PATCH bpf-next v14 0/2] bpf: adding get_fd_path helper Wenbo Zhang
2019-12-18 0:56 ` [PATCH bpf-next v14 1/2] bpf: add new helper get_fd_path for mapping a file descriptor to a pathname Wenbo Zhang
2019-12-18 3:27 ` Yonghong Song
2019-12-19 16:14 ` Daniel Borkmann
2019-12-20 3:35 ` Wenbo Zhang
2020-01-16 8:59 ` Jiri Olsa
2020-02-10 4:43 ` Brendan Gregg
2020-02-11 0:01 ` Daniel Borkmann
2020-02-12 15:21 ` Jiri Olsa
2020-06-01 14:17 ` Wenbo Zhang
2020-06-01 16:38 ` Alexei Starovoitov
2020-06-02 3:04 ` Wenbo Zhang
2020-06-02 8:14 ` Jiri Olsa
2019-12-18 0:56 ` [PATCH bpf-next v14 2/2] selftests/bpf: test for bpf_get_fd_path() from tracepoint Wenbo Zhang
2019-12-18 3:27 ` Yonghong Song
2019-12-17 9:47 ` [PATCH bpf-next v13 " Wenbo Zhang
2019-12-17 16:32 ` Yonghong Song
2019-12-15 4:01 ` [PATCH bpf-next v12 2/2] selftests/bpf: test for bpf_get_file_path() " Wenbo Zhang
2019-12-15 16:24 ` Yonghong Song
2019-12-17 4:01 ` Wenbo Zhang
2019-12-17 4:13 ` Yonghong Song
2019-12-17 9:44 ` Wenbo Zhang
2019-12-05 4:20 ` [PATCH bpf-next v11 " Wenbo Zhang
2019-11-19 13:27 ` [PATCH bpf-next v10 " Wenbo Zhang
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